The primary objective of the proposed research is to test our hypothesis that increased levels of phospholipase activity demonstrated by us in the intestinal tissues of experimentally infected animals are due to inflammation and that the eosinophil is the source of the enzyme. The Trichinella spiralis-mouse model will be used in initial studies, because of abundant information at hand on the intestinal inflammatory responses under a variety of test conditions. Infected and artificially sensitized mice will be studied to relate worm numbers, intestinal inflammation, enzyme levels, and numbers of eosinophils in the bone marrow. Other models will be used in later studies. Studies of the intestine and other tissues will include histologic and histochemical methods and antieosinophil sera to determine the numbers and distribution of eosinophils, and their phospholipase activity in sections, touch preparations, smears, and cell suspensions. The role of phospholipase of eosinophils in the expulsion of worms, its value in monitoring the effects of immunosuppressants, and its role in injuring larvae in the lungs after infection with Nippostrongylus braziliensis also will be studied.